THE  MUSEUM 


OF  THE 


BROOKLYN  INSTITUTE  OF  ARTS  AND  SCIENCES. 

SCIENCE  BULLETIN 

Vol.  i : No.  3. 


THE  ATLANTIC  PALQLO, 


ALFRED  GOLDSBOROUGH  MAYER. 


WITH  ONE  PLATE. 


Published  by  the  Macmillan  Company, 
66  Fifth  Avenue,  New  York. 
December,  1902. 


BY 


Digitized  by  the  Internet  Archive 
in  2016 


https://archive.org/details/atlanticpaloloOOmayo 


THE  ATLANTIC  PALOLO. 


(EUNICE  FUCATA.) 


By  Alfred  Goldsborough  Mayer. 

The  present  paper  has  been  revised  by  my  friend  Professor 
Thomas  H.  Montgomery,  to  whom  I am  indebted  for  valuable  sug- 
gestions. I am  also  grateful  to  Captain  A.  B.  H.  Lillie,  U.  S.  N., 
for  his  kindness  in  granting  transportation  upon  the  Naval  Tug 
“Osceola”  to  and  fro  between  Key  West  and  the  Dry  Tortugas. 

In  1900  I published  a paper*  upon  an  Annelid  whose  breeding 
habits  are  similar  to  those  of  the  well  known  “Palolo”  worm  of 
Samoa  and  Fiji. 

In  this  paper  I made  very  serious  errors  which  were  fortunately 
pointed  out  by  Ehlers,**  Friedlaender,t  and  others. * These  errors 
are  as  follows : I thought  that  the  entire  worm  swam  at  the  surface 
at  the  time  of  the  breeding-swarm,  whereas  in  fact  only  the  sexually 
mature  posterior  segments  swim  at  the  surface,  while  the  whole  an- 
terior part  of  the  worm  remains  below  and  takes  no  part  in  the 
swarm.  The  sexually  mature  posterior  segments  swim  backwards, 
and  what  I described  as  the  “head”  of  the  worm  is  in  reality  the  pos- 
terior segment. 

Moreover,  the  worm  is  Eunice  fucata,  not  a new  species  of  Stauro- 
cephalus  as  I supposed. 

During  the  summer  of  1902  I went  again  to  the  Dry  Tortugas, 
Florida,  in  charge  of  an  expedition  under  the  auspices  of  the  Mu- 
seum of  the  Brooklyn  Institute  of  Arts  and  Sciences,  and  obtained 
hundreds  of  the  worms  in  all  stages  of  growth. 

* An  Atlantic  “ Palolo,”  Staurocephalus  gregaricus,  Bulletin  of  the  Mitseum  of  Com- 
parative Zoology  at  Harvard  College,  Vol.  XXXVI,  p.  1-14,  Plates  I— III. 

**E.  Ehlers,  1901;  Nachr.  Ges.  Wiss.  Gottingen  Math.  Nat.  Cl.,  4 Heft. 

t Benedict  Friedlaender,  1901 ; Biologischer  Centralblatt,  Bd.  XXI,  Nr-  10,  11,  p.  312-317  ; 
352-366. 

t A.  E.  Verrill,  1900;  Trans.  Connecticut  Acad.,  Vol.  X,  p.  650,  proposed  the  generic 
name  “ Mayeria  ” for  the  worm.  This  name  cannot  stand,  for  the  worm  is  a Eunice. 


p 5805 


94  BROOKLYN  INSTITUTE  MUSEUM.  SCIENCE  BULLETIN  : I ; 3. 

Habits  of  the  Atlantic  Palolo. 

The  Atlantic  Palolo  worm  is  Eunice  fucata,  described  and  figured 
by  Elders,  1887.*  It  is  abundant  at  the  Dry  Tortugas,  Florida,  and 
is  recorded  by  Treadwell  from  the  reefs  of  Porto  Rico,t  and  will  prob- 
ably be  found  to  be  widely  distributed  over  the  Bahama  Reefs.  It  has 
not  been  recorded  from  the  Bermudas.  It  lives  within  dead  and  dis- 
integrating coral  rock  or  corroded  coquina,  in  long,  tor.tuous,  smooth- 
walled  burrows  of  uniform  bore;  just  wide  enough  to  accommo- 
date the  worm  itself.  The  animal  commonly  lies ‘coiled  upon  itself 
within  this  burrow,  and  very  often  Polynoe  granulata,  Ehlers,  is 
found  sharing  the  same  burrow  with  the  Palolo.  The  worm  does  not 
live  in  new  and  compact  coral  rock,  or  in  coquina  of  recent  forma- 
tion. It  is,  however,  abundant  in  coral  rock  or  coquina  which  is  dis- 
integrating, and  has  become  infested  with  Pholas,  other  worms, 
Crustacea,  etc.  The  burrow  of  the  Palolo  always  opens  outward  at 
the  surface  of  the  rock  although  as  far  as  I know  the  worm  never 
leaves  its  burrow  permanently  until  the  time  of  the  breeding-swarm. 
Thirteen  rocks  containing  Palolo  worms  were  kept  in  a canvas 
bucket  below  low  tide  level  from  June  24  to  July  28,  1902,  and  dur- 
ing this  interval  they  remained  within  their  burrows.  The  worms 
feed  chiefly  upon  Marine  Algae. 

The  worm  is  common  everywhere  over  the  Tortugas  reefs  from 
immediately  below  low  tide  level  to  a depth  of  at  least  six  fathoms. 
Large  numbers  of  them  are  found  in  the  dead  coral  to  the  westward 
of  Loggerhead  Key  in  N.  Lat.  240  38'  15",  Long.  W.  from  Green- 
wich 82°  56'  30". 


The  Breeding-Szvarm. 

The  Atlantic  Palolo  swarms  within  three  days  of  the  time  of  the 
moon’s  last  quarter  between  June  29- July  28.  The  following  table 
shows  the  dates  of  the  swarms  of  the  years  1898-1900,  1902;  the 
dates  of  the  moon’s  last  quarter,  and  the  period  during  which  the 
ocean  was  watched  continuously,  morning  after  morning. 


*E.  Ehlers,  1887;  Reports  on  the  results  of  Dredging,  etc.,  in  the  Gulf  of  Mexico,  and 
in  the  Caribbean  Sea,  Memoirs  of  the  Museum  of  Comparative  Zoology  at  Harvard  Col- 
lege, Vol.  XV,  p.  91,  Taf.  25,  Fig.  8-20. 

t A.  L.  Treadwell,  1901  ; U.  S.  Fish  Commission  Bulletin  for  1900,  Part  2,  p 196. 


MAYER  : THE  ATLANTIC  PALOLO. 


95 


Year. 

Date  of  the 
Breeding- 
Swarm. 

Date  of 
the 

Moon’s 

last 

Quarter. 

Period  during  which  the  Ocean 
was  observed  continuously 
every  morning  between  4-6 
A.  M. 

Observer. 

1898 

July  9,  10 

July  10 

56  days,  June  25-Aug.  19. . . . 

A.  G.  Mayer. 

1899 

July  1 . 2 

July  29 

49  days,  May  17- July  4 

A.  G.  Mayer. 

1900 

July  19 

July  18 

6 days,  June  19-20,  July  16-19 

Geo.  R.  Billberry. 

1901 

? 

July  8 

4 days,  July  7-10 

Geo.  R.  Billberry. 

1902 

July  24,  25.  28 

July  27 

41  days,  June  19-July  29 

A.  G.  Mayer. 

The  dates  of  the  principal  swarms  are  printed  in  italics. 

The  above  table  shows  that  the  ocean  has  been  watched  continu- 
ously for  146  days  during  the  years  1898,  ’99,  1902,  and  that  no  other 
swarms  of  the  Palolo  appeared  excepting  those  upon  or  near  the 
day  of  the  last  quarter  of  the  June  29-July  28  moon.  Very  careful 
and  prolonged  search  was  made  for  the  worm  during  the  periods  of 
the  June  and  August  last  quarters,  but  without  result  other  than  that 
recorded  in  the  above  table. 

In  1898  great  numbers  of  the  sexual  segments  were  seen  swim- 
ming at  the  surface  before  sunrise  on  the  morning  of  July  9.  On 
July  10,  however,  very  few  worms  could  be  found,  and  after  this 
none  could  be  discovered. 

In  1899  a remarkably  dense  swarm  came  on  the  morning  of  July 
1,  and  only  a few  worms  could  be  found  on  the  morning  of  July  2. 

In  1900  Mr.  George  R.  Billberry,  keeper  of  the  lighthouse  at  the 
Dry  Tortugas,  kindly  watched  for  the  worms  and  having  found 
them  upon  the  morning  of  July  19,  sent  specimens  to  me  preserved 
in  alcohol. 

In  1901,  Mr.  Billberry  again  watched  for  the  worm  from  July 
7-10,  the  last  quarter  falling  on  July  8,  but  he  failed  to  find  the 
worms,  and  we  know  nothing  of  the  swarm  of  1901. 

In  1902,  no  worms  were  to  be  found  until  July  24,  when  they  ap- 
peared in  considerable  numbers.  On  the  morning  of  July  25,  how- 
ever, they  were  much  more  numerous.  None  were  found  after 
careful  search  on  the  mornings  of  July  26  and  27,  but  on  the  morn- 
ing of  July  28,  two  swimming  worms  were  seen,  and  several  hundred 
freshiv  laid  eggs  were  obtained  in  the  tow  net.  No  worms  were  to  be 
found  on  the  morning  of  July  29. 

Description  of  the  Swarm. 

The  sexual  elements  are  confined  to  the  posterior  segments  of 
the  worm.  This  sexual  portion  being  on  the  average  145  mm.  long 
and  composed  of  about  155  segments.  All  but  the  hindermost  25-30 


g6  BROOKLYN  INSTITUTE  MUSEUM.  SCIENCE  BULLETIN  : I ; 3. 

segments  contain  sexual  products.  In  the  male  these  sexual  seg- 
ments are  generally  pink,  while  in  the  female  they  are  dull  sage- 
green  or  brownish  yellow.  These  colors  are  entirely  due  to  the 
color  of  the  contained  sexual  elements,  however,  for  when  the  eggs 
or  sperm  are  discharged  the  swimming  segments  of  both  sexes  are 
dull  brick-red  in  color. 

When  the  swarm  occurs  the  hinder  end  of  the  worm  crawls  out 
backwards  from  the  burrow,  and  attempts  to  swim  away  from  the 
anterior  non-sexual  part  which  remains  within  the  burrow  and  takes 
no  part  in  the  swarm.  A constriction  appears  allowing'  the  sexual 
portion  to  break  away  from  the  anterior  part  of  the  worm ; and 
immediately  the  posterior  end  swims  with  great  rapidity  almost 
vertically  upward  to  the  surface,  upon  reaching  which  it  continues 
to  swim  hind  end  foremost  parallel  with  and  very  near  to  the  sur- 
face of  the  ocean.  This  occurs  at  least  two  hours  before  sunrise 
for  I found  the  Palolo  swimming  at  3.20  A.  M.  on  July  25,  1902. 
The  worms  swim  in  all  directions  and  begin  to  discharge  sperm  or 
ova  through  their  nephropores,  bu^  the  least  stimulus,  such  as  be- 
ing lifted  from  the  water,  or  the  current  from  the  stroke  of  an  oar, 
will  cause  them  to  contract  violently,  often  breaking  themselves  into 
fragments  and  casting  the  sexual  products  out  through  rents  in  the 
cuticula.  This  normally  occurs  as  soon  as  the  first  rays  of  the  sun 
fall  upon  the  water,  and  in  a few  minutes  after  sunrise  all  of  the 
worms  will  have  completely  freed  themselves  of  genital  products, 
and  the  ocean  becomes  milky  in  appearance  due  to  the  vast  quantity 
of  sperm  and  ova  floating  within  it.  The  worms  continue  to  swim  but 
they  gradually  sink  down  and  disappear  so  that  none  are  to  be  seen 
two  or  three  hours  after  sunrise.  In  a dense  swarm  there  may  be 
on  an  average  about  one  worm  per  square  foot  over  wide  areas  of  the 
sea.  The  worms  are  commonest  in  places  where  the  water  is  about  6 
fathoms  in  depth.  Great  numbers  of  the  worms  are  devoured  by 
fishes  as  they  sink,  although  they  are  not  attacked  to  any  great  ex- 
tent while  upon  the  surface.  When  set  free  the  sexual  ends  swim 
vertically  upwards  with  such  rapidity  that  they  run  little  risk  of 
capture,  and  this  habit  must  be  a great  advantage  to  the  worm.  If 
the  swimming  worm  be  broken  into  fragments  each  piece  continues 
to  swim  backward  in  a normal  manner,  showing  that  the  reaction  is 
not  controlled  by  any  one  ganglion  or  localized  group  of  ganglia, 
but  that  the  whole  sexual  end  of  the  worm  is  affected  by  the  stim- 
ulus which  causes  the  breeding-swarm. 


MAYER  : THE  ATLANTIC  PALOLO. 


97 


The  females  are  much  more  sensitive  than  the  males.  Males  may 
readily  be  killed  in  weak  alcohol  or  formalin  without  casting  out 
their  sexual  products,  whereas  it  is  difficult  to  preserve  perfect  fe- 
males in  this  manner.  A count  of  180  worms  collected  at  random 
gave  103  males  and  77  females.  It  appears,  therefore,  that  there 
are  about  57%  of  males  and  43%  of  females. 


Growth  and  Development. 

The  eggs  float  at  or  near  the  surface,  and  are  in  the  4-16  cell  stages 
at  about  7 A.  M.  The  segmentation  is  total  and  unequal,  and  the 
gastrula  is  formed  by  epibole.  The  larva  is  telotrochal,  and  possesses 
two  eyes  and  large  ectodermal  cephalic  glands.  It  swims  through  the 
water  until  four  pairs  of  setigerous  appendages  have  developed,  after 
which  it  sinks  to  the  bottom.  The  development  was  described  in 
detail  by  the  author  in  1900. 

During  June  and  July,  1902,  large  numbers  of  coral  rocks  were 
broken  open  and  many  hundreds  of  the  complete  worms  were  ob- 
tained. The  worms  appeared  to  be  of  two  sizes,  small  slender  ones 
about  90-200  mm.  long,  and  large  stout  ones  250-350  mm.  in  length. 

The  great  majority  were  slender  and  about  200  mm.  in  length  and 
showed  no  signs  of  being  sexually  mature,  while  the  large  worms 
were  all  developing  sexual  products  in  their  posterior  segments. 
Only  about  one  worm  in  a dozen  was  developing  sexual  products, 
and  on  July  28  after  the  last  swarm  I broke  open  a large  number 
of  rocks  and  obtained  43  worms.  Three  of  these  were  of  large  size 
and  their  posterior  ends  were  constricted,  the  sexual  segments  having 
evidently  been  recently  cast  off.  The  constricted  ends  had  healed  but 
no  regeneration  had  taken  place.  (See  figure  7.)  The  remaining  40 
worms  were  140-225  mm.  in  length  and  36  of  them  were  complete, 
two  were  regenerating  at  the  posterior  end  of  the  body,  and  two  had 
recently  lost  the  extreme  posterior  segments  apparently  through  acci- 
dent in  being  cracked  out  of  the  rock,  for  the  ends  had  not  yet 
healed.  All  of  these  40  worms  were  shorter  and  more  slender  than 
those  which  had  evidently  possessed  sexual  segments,  and  none  of 
them  were  sexually  mature.  It  appears,  therefore,  that  the  worm  re- 
quires at  least  two  years  to  attain  sexual  maturity,  and  that  only 
about  one  worm  in  a dozen  gives  rise  to  sexual  segments  in  any  one 
year.  This  may  represent  the  ratio  of  survival  of  the  worms,  only 
about  one  in  twelve  living  to  be  two  or  more  years  old. 


98  BROOKLYN  INSTITUTE  MUSEUM.  SCIENCE  BULLETIN  : I ; 3. 

It  seems  reasonable  to  suppose  that  the  anterior  part  of  the  worm 
regenerates  a new  posterior  end  after  the  swarm.  Many  regenerat- 
ing worms  of  all  sizes  are  found,  and,  indeed,  I had  two  worms 
whose  posterior  ends  were  broken  off  on  June  25,  and  maintained 
them  alive  within  coral  rocks  kept  beneath  low  tide  level  until  July 
28,  and  during  this  period  they  had  regenerated  slender,  tapering  pos- 
terior ends  about  4.5  mm.  long  (see  Figure  6). 

Experiments  on  Fertilization , Etc. 

When  rocks  containing  the  Atlantic  Palolo  are  cracked  open  the 
worm  begins  to  crawl  out  backward,  but  when  about  half  of  the 
length  of  the  worm  has  emerged,  the  anterior  part  attempts  to  re- 
turn into  the  burrow  while  the  posterior  part  struggles  to  swim 
backward.  A constriction  appears  between  the  two  ends,  and  the 
posterior  part  of  the  worm  is  set  free  and  swims  through  the  water, 
while  the  anterior  crawls  back  into  the  rock.  In  large  worms  ' with 
well  developed  sexual  segments  the  break  is  apt  to  appear  exactly  at 
the  junction  between  the  sexual  segments  and  the  non-sexual  ante- 
rior part  of  the  worm.  The  sexual  segments  then  swim  rapidly 
backward  and  upward  to  the  surface,  where  they  continue  to  swim 
backward  with  great  activity.  Soon,  however,  they  begin  to  con- 
tract violently,  casting  sperm  or  ova  out  into  the  water  very  much 
as  in  a normal  swarm.  It  appears  that  the  shock  given  to  the  worm 
upon  cracking  the  rock  acts  as  an  abnormal  stimulus  to  produce  the 
drama  of  the  breeding-swarm,  which  can  be  produced  in  this  manner 
at  any  time  of  the  day.  On  July  12,  17,  19  and  23,  1902,  I obtained 
eggs  and  sperm  from  worms  which  had  thus  been  induced  to  go 
through  with  the  actions  of  a swarm,  but  although  the  sperm  was 
very  active,  and  appeared  to  be  normally  attracted  by  the  eggs,  not 
one  living  embryo  was  obtained,  although  many  of  the  eggs  seg- 
mented abnormally.  It  was  remarkable  that  eggs  obtained  at  4 P.M. 
on  July  23  could  not  be  fertilized  although  less  than  12  hours  after- 
wards the  normal  swarm  occurred  in  which  practically  every  egg  was 
fertilized.  This  is  due  to  the  fact  that  none  of  the  eggs  become  ma- 
ture until  the  time  of  the  normal  swarm  when  all  of  the  eggs  ma- 
ture simultaneously.  Full-grown  female  worms  which  had  dis- 
charged some  eggs  were  killed  on  July  12  and  23,  at  4.30  P.M.,  in  a 
saturated  solution  of  corrosive  sublimate  in  35%  alcohol;  and  four 
females  which  were  swimming  in  the  swarm  at  4.20  A.M.  on  July  24 
were  similarly  treated.  Figure  A shows  the  condition  of  the  eggs 


MAYER:  THE  ATLANTIC  PALOLO, 


99 


in  the  females  killed  on  July  12  and  23.  The  nucleus  is  central  in 
position,  the  nuclear  membrane  is  complete,  and  there  is  a large  nu- 
cleolus. Figure  B,  on  the  other  hand,  shows  the  condition  of  the 
eggs  within  the  females  killed  during  the  swarm  at  4.20  A.M.  on  July 
24.  The  eggs  are  now  about  to  give  oft*  the  first  polar  globule.  The 
nucleus  has  migrated  to  the  surface  at  the  animal  pole,  the  nuclear 
membrane  has  disappeared,  the  nucleolus  has  broken  up  into  small 
spherical  fragments,*  and  the  first  polar  globule  is  not  yet  constricted 
off  from  the  egg. 


I hoped  to  discover  whether  the  Atlantic  Palolo  responds  in  its 
swarm  to  the  light,  or  to  some  attraction  due  solely  to  the  position  of 
the  moon.  Accordingly  a number  of  worms  were  maintained  alive 
within  coral  rocks  beneath  low  tide  level,  and  on  the  nights  of  July 
23-28,  1902,  the  rocks  containing  the  worms  were  placed  in  glass 
aquaria  which  were  shut  up  within  a wooden  boat  shed  into  which 
no  direct  moonlight  could  penetrate.  None  of  these  worms  swarmed, 
but  upon  cracking  open  the  rocks  I discovered  that  all  of  the  worms 
were  immature.  The  experiment  is  therefore  inconclusive  and  should 
be  repeated. 

In  1900  I advanced  the  view  that  the  Palolo  may  be  regarded  as 
an  animal  in  which  the  egg-laying  season  has  been  reduced  to  a 
period  of  one  or  two  days ; and  that  it  could  be  shown  mathematically 
that  a shortening  of  the  egg-laying  period  causes  a greater  concen- 
tration of  breeding  individuals  and  therefore  shortens  the  average 
distance  that  the  spermatozoa  must  travel  in  order  to  fertilize  the 


Fig. A 


Fig.B 


*Not  shown  in  this  individual  section. 


IOO  BROOKLYN  INSTITUTE  MUSEUM.  SCIENCE  BULLETIN  : I ; 3. 

ova.  This  advantage  would  allow  of  an  increase  in  the  relative 
number  of  females  and  a reduction  in  the  number  of  males,  and  thus 
more  eggs  would  be  produced.  The  short  breeding  season  of  the 
Palolo  may,  therefore,  have  been  brought  about  through  the  agency 
of  natural  selection,  provided  the  ancestors  of  the  Palolos  now  living 
possessed  an  initial  tendency  to  swarm  at  or  near  the  period  of  the 
moon’s  last  quarter  rather  than  at  other  times,  and  that  this  tendency 
was  of  a sort  that  would  be  perpetuated  by  inheritance. 

Friedlaender,  1901,  combats  this  view,  holding  that  the  Darwin- 
ian explanation  is  inadequate.  He  maintains  that  the  Palolo  re- 
sponds to  a certain  condition  of  the  tide  in  conjunction  with  an  influ- 
ence which  the  moon  exerts  upon  the  worm  when  at  the  position  of 
last  quarter,  and  that  the  response  of  the  worm  has  not  been  brought 
about  through  natural  selection. 

It  is  interesting  to  observe,  however,  that  the  condition  of  the 
tide  at  the  Tortugas,  Florida,  upon  the  day  of  the  last  quarter  of  the 
July  moon  is  quite  different  from  its  condition  at  Samoa  and  Fiji 
upon  the  days  of  the  last  quarter  of  the  October  and  November 
moons.  At  these  times  in  Fiji  and  Samoa  the  tide  is  about  at  its  low- 
est when  the  sun  rises,  while  at  the  Dry  Tortugas  the  tide  is  ebbing 
but  is  still  about  ipj-2j4  hours  high.  For  example:  On  July 
27,  1902,  at  the  Dry  Tortugas  low  tide  occurred  1 hour  and  22  min- 
utes after  sunrise,  while  at  Apia,  Samoa,  on  October  23  and  No- 
vember 21,  1902,  low  tide  came  at  1 and  at  14  minutes  after  sun- 
rise on  the  respective  dates.  Also  the  mean  rise  and  fall  of  the  tide 
at  the  Dry  Tortugas  is  only  1.1  feet,  while  at  Samoa  and  Fiji  it  is 
2.2 — 3.7  feet.  All  that  we  can  say  is  that  Atlantic  and  Pacific  Palolos 
swarm  upon  or  near  the  day  of  the  last  quarter  of  the  moon,  at  cor- 
responding seasons  of  the  year,  for  the  meteorological  conditions  and 
temperature  of  the  water  at  the  Tortugas  in  July  are  remarkably  simi- 
lar to  those  at  Samoa  and  Fiji  in  October  and  November.  The  worm 
no  doubt  responds  to  some  physical  stimulus  which  is  dependent  upon 
the  condition  or  position  of  the  moon,  but  the  exact  nature  of  this 
stimulus  remains  to  be  discovered. 

Description  of  the  Mature  Worm. 

A minute  description  of  Eunice  fucata  is  unnecessary,  as  the 
worm  has  been  well  described  by  Ehlers,  1887;  Mem.  Mus.  Comp. 
Zool.  at  Harvard  Coll.,  Vol.  XV,  p.  91,  PI.  25.  Ehlers,  however,  had 


MAYER:  THE  ATLANTIC  PALOLO. 


IOI 


access  only  to  alcoholic  specimens,  and  a few  details  may  be  added 
from  an  inspection  of  living-  worms.  The  entire  worm  is  shown  in 
Fig.  i,  the  figure  being  of  natural  size  and  drawn  from  a living  male 
worm  on  June  23,  1902.  The  posterior  sexual  segments  are  not  yet 
fully  developed  and  are  destined  to  become  about  twice  as  long  and 
about  one-half  again  as  wide  as  in  the  figure.  Figure  2 gives  a dor- 
sal, and  Figures  3 and  4 ventral  and  lateral  views  of  the  head,  mag- 
nified four  times.  The  prsestomium  exhibits  a longitudinal  dorso- 
ventral  cleft  dividing  it  into  two  lateral  lips,  each  of  which  bears  a 
pad-like  thickening  on  its  ventral  surface.  The  dorsal  sides  of  the  first 
segment  bear  five  antennae,  one  median  and  four  lateral.  The  eyes 
are  large  and  are  situated  between  the  two  lateral  pairs  of  antennae. 
The  segment  back  of  the  head  bears  no  appendages,  while  the  follow- 
ing segment  bears  only  a pair  of  dorsal  cirri.  In  full-grown  worms 
the  four  succeeding  segments  are  provided  with  lateral  parapodia 
which  lack  gills.  In  younger  worms  there  may  be  five  or  six  of 
these  appendages  without  gills.  The  gills  are,  however,  found  upon 
all  of  the  following  parapodia  of  the  body  excepting  those  of  the 
sexual  segments.  The  gills  of  the  anterior  third  of  the  body  are  the 
best  developed,  and  are  provided  with  7-10  simple  lateral  filaments. 
These  filaments  become  reduced  in  number  back  of  the  first  third  of 
the  worm’s  length  and  in  the  middle  of  the  body  the  gills  have  no 
lateral  filaments  and  are  reduced  to  mere  stumps.  They  disappear 
entirely  at  the  point  of  junction  of  the  body  segments  with  the 
posterior  sexual  part  of  the  worm,  so  that  the  sexual  segments  are 
not  provided  with  gills.  The  external  surface  of  the  gills  is  cov- 
ered with  active  cilia.  The  hindermost  segment  of  the  body  bears 
a pair  of  ventral  cirri.  It  is  interesting  to  observe  that  the  young 
larva  bears  a pair  of  dorsal  as  well  as  a pair  of  ventral  cirri  upon 
its  posterior  segment.  As  the  adult  worms  never  possess  these  dor- 
sal cirri  they  must  degenerate,  leaving  only  the  ventral  pair.  The 
anterior  third  of  the  worm  is  of  a rich  bronze-brown  with  irides- 
cent color  playing  over  it.  The  mid-region  of  the  body  is  duller  in 
color  being  brown  or  brown-red.  The  sexual  segments  are  pink 
or  dull  salmon-yellow  in  the  male  while  in  the  female  they  are 
dull  sage-green  or  dull  brownish-yellow.  These  color  differences 
are,  however,  due  entirely  to  the  color  of  the  contained  sexual  ele- 
ments, for  when  these  are  discharged  the  sexual  segments  of  both 
sexes  become  dull  brick-red  in  color.  The  gills  are  of  a rich  pur- 
ple-red color,  while  the  parapodia  are  light  greenish-yellow.  The 


102  BROOKLYN  INSTITUTE  MUSEUM.  SCIENCE  BULLETIN  : I ; 3. 

worm  is  very  active  in  captivity  and  when  disturbed  will  often  pro- 
trude its  jaws  and  snap  viciously.  Full-grown  worms  are  about 
350  mm.  long.  The  anterior  non-sexual  part  consists  of  about  225 
segments  and  the  posterior  sexual  part  of  about  150  segments. 


Summary. 

The  “Atlantic  Palolo”  is  Eunice  fucata,  Ehlers.  It  is  found  at  the 
Dry  Tortugas,  Florida,  and  lives  within  disintegrating  coral  rock  or 
coquina  from  below  low  tide  level  to  a depth  of  at  least  six  fathoms. 
Its  breeding  habits  are  closely  similar  to  those  of  the  well-known 
Pacific  Palolo  worm  ( Eunice  viridis) . 

The  Atlantic  Palolo  swarms  at  the  surface  before  sunrise  within 
three  days  of  the  day  of  the  last  quarter  of  the  moon  between  June 
29- July  28.  The  posterior,  sexually  mature  end  of  the  worm  breaks 
away  from  the  anterior  end,  and  swims  backwards  and  upwards  to 
the  surface  where  it  continues  to  swim  backward  with  great  rapidity 
until  about  the  time  of  sunrise,  when  it  contracts,  casting  the  genital 
products  out  into  the  water.  The  anterior  part  of  the  worm  remains 
below  in  the  coral  rock.  The  worm  requires  at  least  two  years  to  at- 
tain sexual  maturity.  There  are  57%  of  males  and  43%  of  females. 
Only  sexually  mature  worms  cast  off  their  posterior  ends  at  the  time 
of  the  swarm.  The  immature  worms  are  about  twelve  times  as  nu- 
merous as  the  mature. 

The  shock  produced  by  cracking  the  coral  rock  acts  as  a stimulus 
to  produce  the  drama  of  the  breeding-swarm  before  the  normal  date 
of  the  swarm.  Eggs  obtained  in  this  manner  are  immature  and  can- 
not be  fertilized,  even  twelve  hours  before  the  time  of  the  normal 
swarm.  All  of  the  eggs  mature  simultaneously  at  the  time  of  the 
normal  swarm. 

The  normally  laid  eggs  float  in  the  water  and  begin  to  segment  soon 
after  extrusion  from  the  worm.  The  segmentation 'is  total  and  un- 
equal. the  gastrula  is  formed  by  epibole,  and  the  larva  is  telotrochal. 
The  young  larvae  swim  near  the  surface,  but  sink  to  the  bottom  upon 
attaining  four  pairs  of  setigerous  lobes.  The  posterior  segment  of 
the  larva  bears  a pair  of  dorsal  as  well  as  a pair  of  ventral  cirri. 
Only  the  ventral  pair  of  cirri  persist  in  the  fully  developed  worm. 

Museum  of  the  Brooklyn  Institute  of  Arts  and  Sciences. 
August , 1902. 


LIBRARY 
OT  THE 

UNIVERSITY  of  ILLINOI 


COIOOVYPE  CO.,  K.  V.  C-PI. 


7 


MAYER  ! THE  ATLANTIC  PALOLO. 


% 


J 


103 


Explanation  of  the  Plate. 

Figure  1:  Male  Specimen  of  the  Atlantic  Palolo  Eunice  fucata, 
natural  size.  Drawn  from  life  on  June  23,  1902,  one  month  before 
the  date  of  the  breeding-swarm.  The  sexual  segments  are  not  yet 
fully  developed,  and  finally  become  about  twice  as  long  and  one- 
half  again  as  wide  as  in  this  figure.  (See  Figure  5.) 

Figure  2 : Dorsal  view  of  the  head,  magnified  four  times.  Drawn 
from  life. 

Figure  3:  Ventral  view  of  the  head  showing  the  lip-like  pads  of 
the  prsestomium.  Magnified  four  times. 

Figure  4:  Side  view  of  the  head.  Magnified  four  times. 

Figure  5 : Sexually  mature  swimming-segments.  Natural  size. 
Drawn  from  a specimen  found  upon  the  surface  of  the  sea  at  4.20 
A.M.,  on  July  25,  1902.  The  hind  end  is  represented  above  and  the 
constricted  anterior  end  below.  The  hind  end  is  always  directed  for- 
wards in  swimming. 

Figure  6:  Showing  the  amount  of  regeneration  which  took  place 
at  the  broken  posterior  end  of  a worm  between  June  25- July  28. 
The  figure  is  three  times  natural  size. 

Figure  7 :*  The  constricted  posterior  end  of  the  non-sexual  ante- 
rior part  of  the  Palolo.  Found  on  July  28,  two  or  three  days  after 
the  posterior  sexual-segments  had  been  constricted  ofif.  No  regen- 
eration-is.  as  yet  apparent  although  the  last  remaining  segment  has 
contracted  and  the  wound  has  completely  healed.  This  figure  shows 
the  swollen  transverse  ridges  which  are  peculiar  to  the  mid-dorsal 
tract  of  the  worm.  The  figure  is  two  and  one-half  times  natural 
size. 

Figures  I,  IV,  V,  and  XIX : The  first,  fourth,  fifth  and  nineteenth 
parapodia  respectively.  The  first  four  pairs  of  parapodia  lack  gills. 
The  fifth  possesses  a small  gill  with  two  lateral  filaments.  These 
lateral  filaments  increase  in  number  and  there  are  7-10  of  them  upon 
the  parapodia  of  the  anterior  third  of  the  worm’s  length,  as  is  shown 
in  the  figure  of  the  nineteenth  parapodium. 


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